This short study was written during my tenure of a Travelling Studentship from the National University of Ireland, and in March, 1920, was accepted for the Research Degree Certificate of Cambridge University.

A glance at the bibliography shows that comparatively little has been written in English on this interesting period of our history. On the other hand modern Scandinavian scholars—Alexander Bugge, Marstrander, and Vogt—have thrown a good deal of light on the subject, but unfortunately very few of their books have been translated into English. The present dissertation is based principally upon the Old and Middle Irish annals and chronicles and the Icelandic sagas; reference has also been made to the work of Scandinavian, English and Irish scholars on the subject.

I should like to acknowledge my debt to Professor Chadwick, who directed my work: those who have had the privilege of working under him will readily understand how much is due to his encouragement and stimulating criticism. I wish also to express my thanks to my friends, Miss N. Kershaw and Mr. E. J. Thomas, for many kindnesses while the book was in preparation; to Miss Eleanor Hull and Professor Ó’MÁille, University College, Galway, for the loan of books; and to the Librarian and staff of Cambridge University Library, the National Library, Dublin, and T.C.D. Library.

A. W.